1. Field of the Invention
The invention relates to an optical device for medical endoscopes or technical (engineering) endoscopes e.g. for examining visually the inside of an object such as a car engine, and more particularly to such an optical device of the kind comprising an inner tube which holds the optical system and is situated in an outer tube, the outer tube being rigidly connected at its proximal end part to a sleeve of enlarged internal diameter which is connected to an eyepiece and through which the inner tube passes.
2. Description of the Prior Art
In the known optical devices of the aforementioned kind of endoscopes, on the one hand the outer tube is rigidly connected to the distal part of the wide sleeve and on the other hand the inner tube is rigidly connected to the proximal part of the wide sleeve, e.g. by soldering. However, if for medical reasons sterilisation with superheated steam at 134.degree. C has to be performed or, in the case of engineering endoscopes, if they have for example to be inserted through sparking-plug holes in order to examine the insides of the cylinders of engines while they are still hot, differing amounts of expansion occur between the widened sleeve connected to the outer tube and the inner tube, which is also rigidly connected to the sleeve. This difference in expansion sets up stresses which may give rise to fractures, particularly at the soldered joints.
The main object of the present invention is, therefore, to compensate for the difference in expansion of the metal parts of the optical device.